1. Field of the Invention
The present invention relates to a magnetic bubble memory device having functions using ion-implanted tracks and conductor patterns, and relates more particularly to functions of a block replicate gate and a swap gate.
2. Description of the Related Art
A magnetic bubble memory device having functions using ion-implanted tracks and conductor patterns has been disclosed, for example, in IEEE, Trans. Magnetics, MAG 20, 1984, pp. 1072-1074. The memory device has a major=minor loop structure as shown in FIG. 1, wherein a gate 6 between a major loop 2 and a minor loop 5 has only transfer-out and transfer-in functions to output and input magnetic bubbles,respectively. A memory device employing permalloy tracks shown in FIG. 2, on the other hand, has a block replicate gate 7 which divides the magnetic bubble in the minor loop 5 into two bubbles and takes them out onto a read major line 10, and has a swap gate 8 which exchanges the magnetic bubbles in the minor loop 5 with the magnetic bubbles on a write major line 9. The two kinds of the gates make it possible to greatly reduce the cycle time in read and write operation.
With reference to the block replicate gate 7 of FIG. 2, adesign has been proposed in which upper and lower conductor patterns are formed on the ion-implanted tracks as shown in Trans., Magnetics, MAG-20, 1982, pp. 1087-1089. With reference to the swap gate 8, there has been proposed a design employing a single layer conductor as disclosed, for example, in Japanese Patent Laid-Open No. 155590/1983. However, two problems arise as described below if the memory chip architecture as shown in FIG. 3 is used. In the architecture, the two kinds of gates are connected to the upper and lower corners in the minor loop and are also connected to the write major line and to the read major line, respectively. The first problem is that either the write major line 9 or the read major line 10 has poor bubble propagation characteristics. The problem comes from the fact that the easy magnetic axis of the ion-implanted layer has a three fold symmetry. The second problem is that the two major lines have bubble propagation directions that are opposite to each other as designated at 11 and 12 in FIG. 3. Therefore, the output data stream in the read operation is the inverted data stream of the input data stream in the read operation.
No system has yet been proposed that is effective to solve these two problems. The memory device having ion-implanted functions of both the block replicate gate and the swap gate has not yet been realized, which results in no compatibility to the existing permalloy devices.